10 April 2015
Here are two maps showing the temperatures at 5 Am and 4 PM. Many areas saw a rise of over 34 degrees in just a few hours today. This rapid change in temperature was made possible by two things. Ocean and elevation. At sunrise a chilly easterly wind off the cold Atlantic (where water temps are only around 42 degrees) had pushed all the way to the Blue Ridge Mountains of Virginia. This deep layer of marine air was characterized by low stratus clouds, fog and even some thick drizzle. Then it all dramatically changed!
As a cool front approached from the west this afternoon, the winds turned to the southwest causing the air to flow down hill (from elevations of nearly 3200 feet to sea level). The air was compressed due to the higher pressure and it warmed. Air being compressed like this will rise about 10 degrees Celsius per 1000 meters ( 16.5 degrees per 3,000 feet). This brought soaring temps to Maryland, Delaware, and Tidewater Virginia, with some spots passing 80 degrees.
In rare cases adiabatic compression can cause temperatures to soar in a matter of minutes, and this is called a heat burst. I experienced one of these rare events in Oklahoma a decade ago, when the temperature soared twenty degrees in under a minute! There was also one last summer in Kansas that was well documented. Physics works!